Apparatus for distributing solids



United States Patent O 4 Claims. (Ci 21 4-1838 The present inventionrelates to an apparatus for distributing dusty to pulverulent orgranular solids or mixtures of such solids in uniform thin layers, forexample l-grain layers.

Chemical processes carried out with one or more solid reactionComponents which must be applied in a fairly thin layer in order toenable the absorption of further reaction Components or the supply ofenergy require dis tributng apparatus which ensure the achievng ofanappropriate thin and uniform layer. The common and known distrbutingapparatus are based on the principle of stripping. This principle,however, cannot be applied to reaction masses that cannot be moved.Rotary plates which distribute the solids over large circular areas bycentrifugal force are also widely used. These plates have thedisadvantage of having a very great indefinite scattering angle in theflight path of the solids at a constant rotational speed so that toogreat a classification of the different grain sizes takes place. Thisundesirable separation into Components is particularly pronounced whentwo or more solids of different specific gravity are distributed.

The present invention provides a process for distributing solids in thinlayers, for example l-grain layers, which enables the aforesaiddisadvantages to be overcome.

According to the process of this invention, dusty to pulverulent orgranular solids or mixtures of such solids are introduced through a tubewhich is disposed above the center of 'a circular curved or planereceiving surface and is at a certain distance from said center androtates about its vertical longitudinal axis at a periodically variablerate of revolutions. The tube is charged from above. The lower end ofthe tube is defiected or curved. The direction in which the solids areintroduced as well as the distance between the point of introduction andthe center of the receiving surface are thus continually andperiodically varied, whereby the material is distributed in extremelythin layers.

into the straight part of the upright rotary tube a stationary tube ofsmaller diameter may be inserted from above and used for feeding thesolids to the lower defiected end of the outer rot-ary tube.

The apparatus of this invention may be used, for example, in thefollowing manner: the rotary tube is inserted from above into a Chemicalreaction furnace, in which case it is used for charging the reactionfurnace with the material to be reacted. In the zone Where the rotarytube enters the reaction furnace, the rotary tube may be surrounded withat least one cooling jacket and/ or an insulating layer. The devices forinserting and supporting the rota'y tube into the reaction furnace maybe vacuum-tght if desired and are advantageously con structed in amanner such that the rotary tube can be easily exchanged.

The following remarks are made with regard to execution of the processof the invention:

When the rotary tube which is used as feeding device in the process ofthe invention is charged from above with solids, the latter aredistributed at a scattering angle of about 5 to 6 over a circular ringsurface. By causing the tube to rotate at a periodically varying rate ofrevolutions, the solids are distributed in layers of uniform thickthe&lh-?h Patented June 22, 1965 ness over circula' ring areas whichaccurately adjoin one another so that a circular area is obtained whichis uni formly covered with the material with the exception of the centerdirectly beneath the distributing tube. This small uncovered center maythen be directly covered with the material without distribution.

To distribute the solids over adjoining circular ring areas isespecially advantageous when two or more solids of different specificgravity are used. The undesired separation of different solids is maskedand neutralized by continuously adjoining to one another severalcircular ring areas in accordance with the invention.

In order to avoid formation of undesired centrifugal forces in tubes oflarge diameters, for example of an inside diameter exceedingmillimeters, which centrifugal forces prevent the solids from fallingdown, a stationary tube may be axially inserted in the straight part ofthe rotary tube as already mentioned above, the stationary tubeextending from above to the lower curved end of the rotary tube. i

The present invention enables the distribution of solids in layershaving a thickness ranging from the grain size in a given case to amultiple thereof. It is even possible to proceed in a manner such thatnot the whole surface over which the solids are to be distributed iscovered in each period with an uninterrupted unform layer but that onlya part of this surface is covered with fresh solids in each period sothat several periods are required for covering the whole surface withone layer, that is to say, the rate of revolutions rnay be varied sorapidly and controlled in a manner such that the receiving surface iscompletely covered only after several periods.

The distributing tube of this invention can be used for the uniformdistribution of solids in open or closed ap- -paratus at temperatures upto about +2500 C. under normal pressure, superatmospheric pressure orreduced pressure. Processes in which a great amount of energy has to besupplied at high temperatures to heat-insulating reaction mixtures whichare in the solid state, can only be carried out at the rapid speed ofConversion necessary in industry when the reaction mixture is applied inuniform and fairly thin layers without separation taking place. Thethinner the layer, the greater is the energy absorption per unit ofsurface. The apparatus of the present invention enables thisidefineddistribution to be realized in an excellent manner.

An apparatus suitable for use in carrying out the process of thisinvention is illustrated diagrammatically by way of example in theacconpanying drawing wherein:

FIG. l is a sectonal view of one embodiment of this invention; and

FIG. 2 is an enlarged view of a portion of the embodiment shown in FIG.1.

Reterring to the drawing, a reaction and vacuum furnace is designatedby 1. The material to be reacted is in the lower part of the reactionchamber of the furnace 1, while the electrodes 12 project into the upperpart thereof. The reaction chamber is connected with the vacuum pump byoutlet pipe 13. Slot 16 surrounding the zone in which the electrodes areled through the wall of the furnace serves for the introduction ofhydrogen. The material that has been reacted is removed by way ofmovable grate 7 provided at the bottom of the reac tion furnace.

The solids to be reacted which may be in a dusty, pulverulent orgranular form are supplied through a feeding device ntroduced at thehead of the reaction furnace 1. This feeding device consists of arotatable feed tube 8 into which the material is introduced from above(arrow lt?) through inner tube 10' which is shown in FIG 2. The lowerend 3 of the tube is curved and provided with an outlet 2 through whichthe material to be reacted leaves the tube in order to be finelydistributed over the circular surface of material 6 lying beneath.

The rotary tube 8 is surrounded with a double cooling jacket 9 which isbent at its one end to conform to elbow 3 of tube 8. At a certaindistance therefrom, a stationary double cooling jacket is disposed whichis surrounded with an insulating layer 4 in the zone where the rotarytube 8 enters the hot reaction chamber. The rotary tube 8 is led throughthe bearings 11. It is introduced into the reaction chamber through theaperture 14 forrned by the short connecting pipe 15 and can also beremoved through this aperture 14 in an upward direction.

The following example serves to illustrate the invention but it is notintended to limit it thereto:

Example Into a reaction furnace 1 for the manufacture of magnesium vaporfrom burnt dolomite of a grain size of 1 to millimeters and granularferrosilicon of strength having a grain size of 0.5 to 5 millimeters ata temperature of 1500 to 1700 C. under a redueed pressure of about 1 to100 millimeters of mercury, the reaction Components are continuouslydistributed in a thin layer over the mixture that has already reacted.The material is distributed in accordance with the invention through therotary tube 8 which is disposed vertically above the center of thereaction surface and the lower end of which is deflected. The tube hasan inside diameter of about millimeters and a length of 3 meters. Thelower end of the tube is defiected over a length of 20 centimetersthrough an angle of about C. in a curve. The rotary tube 8 is providedover its entire length with a double cooling jacket 9 for cooling water.

The rotary tube is insulated against the heat prevailing in the furnaceby a stationary heat insulating jacket 4 which is cooled at its insidewall by a double cooling jacket 5 through which a cooling liquid ows.

The rotary tube 8 is driven :at a speed which is continuously varied inpredetermined periods and passes in about 2 minutes through all numbersof revolutions in the range of 40 revolutions per minute to revolutionsper minute, the rate of revolutions increasing and deereasing. Theincrease and decrease of the rate of revolutions is controlled by acontrol disk in a manner such that per period of time of 2 minutes onlyone fifth of the circular reaction surface 6 having a diameter'of 5.5meters is covered with fresh material. In the following periods of timeof 2 minutes each the remaining portions of the surface are covered sothat in a prolonged time the reaction mixture grows absolutely uniformlyand a maximum energy is consequently transmitted by the electrodes 12.

To obtain particularly high yields of material, the process isadvantageously carried out in such a manner that after a period of timeof about 10 minutes a complete l-grain layer has just been distributed.

The mixture that has been reacted is removed in a downward direction bymeans of a movable grate 7, the removal taking place gradually as freshreaction mixture is introduced.

It should be emphasized that when a mixture of dolomite and ferrosiliconis distributed the dolomite and ferrosilicon have a pronounced tendencyto separate due to their different specific gravity. Only by the factthat the separation is masked and neutralized by the continuousadjoining of several circular ring areas in accordance with the processof the invention is it ensured that no losses occur in the reaction ofthe costly reducing agent.

In the preceding example the dolomite flies farther to the wall of thefurnace than the ferrosilicon which is simultaneously introduced. Owngto this fact, a narrow marginal zone poor in ferrosilicon is formedwhereby the reaction mixture is prevented in an advantageous manner fromcaking on the walls of the furnace.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. lt is, therefore, to beunderstood that within the scope or" the appended claims the inventionmay be praeticed otherwise than as specifically described.

I claim:

1. An apparatus for distributing solids uniformly in thin layers ontoand over the entire surface of a circular shaped area of a reactionfurnace chamber which comprises a tube arranged substantially verticallyand monnted for rotation about its longitudinal axis, the lowerdischarge end of said tube being curved outwardly away from its verticalaXis, a stationary tube disposed within the rotatable tube and extendingthe length of the straight part thereof, the upper end of the stationarytube being adapted to receive granular or pulverulent materials, andmeans to rotate the rotatable tube at varying rates over a predeterminedperiod of time.

2. An apparatus as claimed in claim 1 wherein the rotary tube isintroduced from above into a furnace reaction chamber. I

3. An apparatus as claimed in claim 2 wherein the rotary tube issurrounded with at least one cooling jacket and an insulating layer inthe zone where the rotary tube enters the reaction furnace chamber.

4. An apparatus as claimed in claim 2 wherein the rotary tube isprovided with bearings including a vacuumtight seal.

References Cited by the Examiner UNITED STATES PATENTS 2,2l5,736 9/40Jones 193--3 2,320,206 5/43 Engel et al. 266-27 2,654,594 10/53 Somogyi266-27 2,713,408 7/55 Tench 193-3 i FOREIGN PATENTS 738,584 8/43Germany.

749,557 11/44 Germany.

777,266 6/ 57 Great Britain.

MORRIS O. WOLK, Primary Examiner.

RAY K, WINDHAM, MARCUS U. LYONS Examiners.

1. AN APPARATUS FOR DISTRIBUTING SOLIDS UNIFORMLY IN THIN LAYERS ONTOAND OVER THE ENTIRE SURFACE OF A CIRCULAR SHAPED AREA OF A REACTIONFURNACE CHAMBER WHICH COMPRISES A TUBE ARRANGED SUBSTANTIALLY VERTICALLYAND MOUNTED FOR ROTATION ABOUT ITS LONGITUDINALLY AXIS, THE LOWERDISCHARGE END OF SAID TUBE BEING CURVED OUTWARDLY AWAY FROM ITS VERTICALAXIS, A STATIONARY TUBE DISPOSED WITHIN THE ROTAT-